1. Field of the Invention
The present invention relates to an optical modulator for modulating a light beam irradiated by a light source in accordance with image information, and an optical device and a projector having the optical modulator.
2. Description of Related Art
Conventionally, a projector having a light source, an optical device for modulating a light beam irradiated by the light source in accordance with image information and a projection optical system for enlarging and projecting the light beam modulated by the optical device has been known as an optical equipment using an optical device (see Japanese Patent Laid-Open Publication No. 2000-89364).
The optical device of the projector has three optical modulators for modulating color light in accordance with image information, and a color combining optical system for combining respective light beams modulated by the optical modulators to form an optical image.
The optical modulator has an optical modulator body having a pair of substrates sealing an electrooptic material such as liquid crystal therebetween and a holding frame for accommodating and holding the optical modulator body.
The pair of substrates of the optical modulator body includes a first substrate on which a data line, a scan line, a switching element, a picture electrode etc. for applying driving voltage to the electrooptic material are formed, and a second substrate on which a common electrode, a black mask, and a color filter as necessary are formed.
The holding frame has an accommodating portion for accommodating the optical modulator body, and a fixing plate for positioning the optical modulator body inside the accommodating portion. The optical modulator body is accommodated in the holding frame with one of the substrates facing to the side of the accommodating portion of the holding frame and, subsequently, the optical modulator body is pressed by the fixing plate from the side of the other substrate.
In such optical modulator, the data line and scan line formed on the first substrate and the black mask formed on the second substrate etc. absorbs the heat generated by irradiating the light beam from the light source, thereby raising the temperature of the first and the second substrates. Accordingly, the heat of the substrates has to be released.
The substrate disposed on the accommodating portion side contacts with the accommodating portion on a large area, the heat can be efficiently released by constructing the accommodating portion with a heat-conductive material such as metal.
However, heat of the substrate located on the side of the fixing plate cannot be efficiently released, because the fixing plate is constructed by a thin plate and therefore has small heat capacity and the fixing plate only partially contacts with the substrate to press and hold the substrate.
Though it is possible to thicken the fixing plate to increase the heat capacity of the fixing plate, such arrangement inevitably increases the thickness of the optical modulator and the size of the optical device provided with the optical modulator, so that size reduction cannot be achieved. Further, since the gap against an optical element disposed on the downstream of the optical modulator such as a polarization plate is enlarged, image quality such as color evenness and contrast may be deteriorated.
An object of the present invention is to provide an optical modulator without deteriorating image quality and capable of improving heat releasing ability of the substrate, an optical device and a projector having the optical modulator.
An optical modulator according to an aspect of the present invention modulates a light beam irradiated by a light source in accordance with image information, the optical modulator including: an optical modulator body having a pair of transparent substrates between which an electrooptic material is sealed; a holding frame having an accommodating portion that accommodates the optical modulator body and a fixing plate that presses and holds the optical modulator body within the accommodating portion; and a frame member made of a heat-conductive material and provided on an outer periphery of a first substrate of the pair of substrates disposed on the side of the fixing plate, the frame member being in contact with the accommodating portion and/or the fixing plate.
The frame member may only be in contact with the accommodating portion of the holding frame or may only be in contact with the fixing plate. Alternatively, the frame member may be in contact with both of the accommodating portion and the fixing plate.
According to the above arrangement, since the frame member made of heat-conductive material is disposed on the outer periphery of the fist substrate of the optical modulator, the heat of the first substrate can be efficiently transferred to the frame member. Since the frame member is in contact with the holding frame, the heat transferred to the frame member is released to the outside through the holding frame. The provision of the frame member made of heat-conductive material allows efficient heat releasing from the first substrate to the holding frame, thus enhancing heat-releasing ability of the first substrate.
Further, since excellent heat-releasing ability can be obtained by providing the frame member, there is no need for increasing the thickness of the fixing plate in order to increase the heat capacity of the fixing plate, thus avoiding deterioration of image quality.
In the optical modulator of the above aspect of the present invention, the fixing plate and the frame member may preferably be integrally formed.
The fixing plate and the frame member may be integrated after constructing separate components and bonding the components with an adhesive etc. or may be integrated by welding etc. Alternatively, the fixing plate and the frame member may be an integrated molding formed by injection molding process etc.
According to the above arrangement, since the frame member made of heat-conductive material is disposed on the outer periphery of the first substrate of the optical modulator, the heat generated on the first substrate can be efficiently transferred to the frame member. Further, since the frame member is formed integrally with the fixing plate, sufficient contact area between the frame member and the fixing plate can be secured, thus releasing the heat generated on the first substrate toward the outside through a heat conduction channel from the frame member to the fixing plate. Accordingly, heat-releasing ability of the optical modulator body can be improved, thus lengthening the life of the optical modulator. Further, since the heat-releasing ability of the optical modulator body can be enhanced, there is no need for increasing the thickness of the fixing plate to increase the heat capacity of the fixing plate, thus avoiding deterioration of image quality.
In the optical modulator of the above aspect of the present invention, the fixing plate and the frame member may preferably be made of a heat-conductive metal or a heat-conductive resin.
The heat-conductive metal may be steel-nickel alloy such as Invar and 42Nixe2x80x94Fe, magnesium alloy and aluminum alloy.
The heat-conductive resin may be a resin (polycarbonate, polyphenylene sulfide, liquid crystal resin etc.) containing carbon filler such as carbon fiber and carbon nanotube.
According to the above arrangement, since the fixing plate and the frame member are made of heat-conductive metal or heat-conductive resin having excellent heat conductivity, the heat-releasing ability of the first substrate can be further enhanced by the heat conduction channel.
In the optical modulator according to the above aspect of the present invention, the thermal conductivity of the heat-conductive metal and the heat-conductive resin may preferably be not less than 10W/(mxc2x7K).
According to the above arrangement, the heat generated on the first substrate can be rapidly released through the heat conduction channel. Further, the material of the fixing plate and the frame member can be freely selected as long as the thermal conductivity thereof is not less than 10W/(mxc2x7K), so that the most appropriate material can be selected in designing the optical modulator in accordance with required performance etc.
In the optical modulator according to the above aspect of the present invention, the frame member may preferably be accommodated and held in the accommodating portion together with the optical modulator body and a predetermined gap may preferably be secured between the outer circumference of the frame member and the inner circumference of the accommodating portion.
According to the above aspect of the present invention, since a predetermined gap is secured between the outer circumference of the frame member and the inner circumference of the accommodating portion, mechanical interference generated between the frame member and the accommodating portion on account of difference in thermal expansion caused by different thermal expansion rate can be prevented even when the frame member and the accommodating portion are made of different components. Accordingly, distortion generated on the optical modulator on account of the heat generated on the optical modulator body can be avoided, thus preventing deterioration in image quality on account of change in the shape of the electrooptic material sealed between the pair of substrates.
In the optical modulator according to the above aspect of the present invention, a dust-proof glass that prevents adhesion of dust on the outer surface of the substrate may preferably be closely attached on the outer surface of the first substrate, and the frame member may preferably be in contact with the dust-proof glass and/or the first substrate.
The frame member may only be in contact with one of the dust-proof glass and the first substrate, or may be in contact with both of the dust-proof glass and the first substrate.
According to the above arrangement, when the frame member is only in contact with the first substrate, since the heat of the first substrate can be directly transferred to the frame member, the heat of the first substrate can be efficiently released.
Further, when the frame member is only in contact with the dust-proof glass, the heat of the first substrate is transferred to the frame member through the dust-proof glass and is released through the heat conduction channel. Since the frame member is made of heat-conductive material, the heat can be efficiently transferred from the dust-proof glass to the frame member. Accordingly, even when the frame member is only in contact with the dust-proof glass, excellent heat-releasing ability of the first substrate can be obtained.
When the frame member is in contact with both of the dust-proof glass and the first substrate, since the heat can be transferred from both of the dust-proof glass and the first substrate to the frame member, the heat-releasing ability of the first substrate can be further enhanced.
In the optical modulator according to the above aspect of the present invention, the dust-proof glass may preferably be made of any one of materials selected from the group consisting of sapphire, quartz, crystal or fluorite.
According to the above arrangement, high thermal conductivity can be applied to the dust-proof glass made of light-transmissive material. Accordingly, the heat-releasing ability of the first substrate can be enhanced by arranging the dust-proof glass with such material.
In the optical modulator according to the above aspect of the present invention, a heat-conductive adhesive may preferably be filled in the predetermined gap and between the frame member and the dust-proof glass and/or the first substrate.
According to the above arrangement, since the heat-conductive adhesive is filled in the gap formed between the outer circumference of the frame member and the inner circumference of the accommodating portion, the adhesive assists heat transfer between the respective components, so that heat conduction channel from the frame member to the accommodating portion as well as the heat conduction channel from the frame member to the fixing plate can be secured, thus further improving heat-releasing ability of the first substrate.
Further, since the adhesive having thermal conductivity is filled between the frame member and the dust-proof glass and/or the first substrate, the adhesive assists heat transfer between the respective components, so that the heat generated on the first substrate can be further rapidly released through the heat conduction channel from the frame member to the fixing plate.
In the optical modulator according to the above aspect of the present invention, the adhesive may preferably contain a metal material.
According to the above arrangement, since the metal material thermally couples the components when the adhesive is sandwiched between the components, heat transfer between the components can be further accelerated.
In the optical modulator according to the above aspect of the present invention, a linear expansion coefficient of the fixing plate and the frame member may preferably be not more than 6*10xe2x88x926/K.
According to the above arrangement, since the linear expansion coefficient of the fixing plate and the frame member becomes close to the linear expansion coefficient of the dust-proof glass and/or the first substrate, variation in dimension (expansion and contraction) of the fixing plate and the frame member and the dust-proof glass and/or the first substrate caused by heat can be made approximately equal. Accordingly, when the fixing plate and the frame member are fixed to the dust-proof glass and/or the first substrate by an adhesive, distortion generated on the optical modulator on account of change in the dimension of the respective components can be prevented, and deterioration in image quality on account of change in the shape of the electrooptic material sealed between the pair of substrates can be avoided.
In the optical modulator according to the above aspect of the present invention, the plurality of data lines arranged mutually in parallel, a plurality of scan lines arranged in a direction orthogonal with the plurality of data lines, a picture electrode, and a switching element disposed between the data and the scan lines and the picture electrode may preferably be formed on the first substrate.
Such scan lines and data lines are likely to absorb the heat generated by irradiating the light beam from the light source and the temperature of the substrate with the scan lines and the data lines formed thereon is easy to rise.
According to the above arrangement, since the fixing plate integrated with the frame member is located on the side of the first substrate, the heat generated on the optical modulator body can be efficiently released.
In the optical modulator according to the above aspect of the present invention, the first substrate may preferably be disposed on a light-irradiation side of the optical modulator body.
Since polarization plate located on the downstream of the optical modulator and prism are attached on the light irradiation side of the optical modulator body, heat-releasing ability of the light-irradiation side is inferior.
According to the above arrangement, since the fixing plate integrated with the frame member is located on the side of the first substrate located on the light-irradiation side, the heat-releasing ability can be enhanced.
An optical device according to another aspect of the present invention has: a plurality of optical modulators that modulates a plurality of color lights in accordance with image information respectively for the color lights; and a color combining optical device that combines the color lights modulated by the respective optical modulators, in which the optical modulator is the above-described optical modulator.
According to the above aspect of the present invention, since the optical device has the above-described optical modulator, the same effects and advantages as the above-described optical modulator can be obtained. In other words, an optical device causing no deterioration in image quality and having excellent heat-releasing ability from the substrate can be provided.
A projector according to still another aspect of the present invention forms an optical image by enlarging and projecting a light beam irradiated by a light source after modulating the light beam, the projector having the above-described optical modulator or the above-described optical device.
According to the above arrangement, the same effects and advantages as the above-described optical modulator and the optical device can be applied to the projector.
Further, since the projector has the optical modulator and the optical device having excellent heat-releasing ability, when a fan is used to cool the optical modulator and the optical device, the size and noise of the fan can be reduced.
Further, since the projector has the optical modulator and the optical device having excellent heat-releasing ability, the light beam from the light source can be intensified, thus increasing the brightness of the image projected on a screen.